At the initiation of the takeoff roll, following a touch-and-go landing, the student pilot added full power, but before she could rotate for takeoff, she experienced "… a hard time controlling the airplane on the ground." She therefore aborted her takeoff, but was unable to keep the airplane from departing the side of the runway, where it impacted a distance remaining sign. As a result of the collision, one of the main landing gear separated. An inspection of the airplane did not reveal any anomalies with the nose wheel steering or rudder systems.